1874.] 



1(55 



[Outerbridge. 



natural scale. Further modifications of this principle suggested them- 

 selves and were tried with indications of valuable results. (Fig. 1.) 



By using as one electrode, an alloy of gold and copper of comparative 

 fineness, and a baser alloy of the same metals as the other electrode, a 

 result not before observed presented itself. The lines of both copper and 

 gold crossed the entire field of vision, but in the section representing the 

 fine alloy, the gold lines were strong and bright, while in the section rep- 

 resenting the base alloy the gold lines were very faint. (Fig. 2.) 



By now gradually increasing the distance between the electrodes, the 

 faint gold lines of the base alloy cease to join their bright counterparts 

 of the fine metal at the central line. (Fig. 3.) 



The intervening space is at first minute, but as the electrodes are 

 further separated, the ends of the faint lines gradually recede towards 

 the outer edge of the spectrum until they finally disappear altogether. 

 A scale was constructed of the distances at which the electrodes were 

 withdrawn during the several trials, and careful notes were made, but 

 time did not permit an elaboration of these experiments by accurately 

 testing the results when alloys of approximate fineness formed the elec- 

 trodes. I had wished to use a spectroscope of greater dispersive power, 

 (in order to observe as many distinct lines as possible), and also to 

 magnify the lines by projecting the spectrum through a lantern upon a 

 screen. 



